Chemical analysis tools such as gas chromatographs (“GC”), mass spectrometers (“MS”), ion mobility spectrometers (“IMS”), and various others, are commonly used to identify trace amounts of chemicals, including, for example, chemical warfare agents, explosives, narcotics, toxic industrial chemicals, volatile organic compounds, semi-volatile organic compounds, hydrocarbons, airborne contaminants, herbicides, pesticides, and various other hazardous contaminant emissions. Mass spectrometers measure the atomic mass of a material's constituent molecules and report the masses of these molecules and their relative abundance. This information is used to identify the material. Mass spectrometers may be considered the gold standard for chemical analysis.
As chemical analysis has become a more routine part of many industries, a need has developed for smaller, lighter mass spectrometers that can be incorporated more easily into laboratory and industrial settings and that have lower initial instrument costs and continued operating costs. Additionally, there is a need for portable mass spectrometers that may be used to detect analytes in the field, that have low power requirements and a small size. There are, however, physical limits to the miniaturization of mass spectrometers.
Conventional mass spectrometers may include an ion source, an ion trap, and an ion detector. In smaller devices, these components may be encased within a chamber having an interior volume of approximately 30 cm3. In some instances, the ion detector can occupy more chamber space than the ion source and the ion trap combined.
The location of the ion detector within the chamber can be problematic. For example, the output signal of the detector may be subject to the high voltage RF signal applied to the ion trap. This may result in noise or corruption of the detector signal. Further, the electrical connections required to output the detector signal to processing equipment can add to the size, complexity, and cost of mass spectrometers.
The ion detector typically operates under a vacuum environment, requiring pressures in the range of 10−3 to 10−8 Torr for proper operation. Mass spectrometers thus employ pumps, often a system of vacuum pumps, to achieve these pressures, which account for the size and cost of mass spectrometers. The size of the chamber and the corresponding pump system are often limiting factor on the ability to further reduce the size of conventional mass spectrometers.
The size of the chamber has other drawbacks. Because of the relatively large interior volume of the chamber, low volatility compounds such as, for example, explosives and narcotics, may stick to surfaces of the chamber and remain in the chamber after use. These chemicals may outgas slowly and create false leaks or detections, which can be problematic.
Additionally, the large volume of the chamber, as compared to the small volume of the ion trap, means that only a small fraction of the analyte introduced to the system is trapped and analyzed. As a result, the overall sensitivity of the system is reduced. This is an issue where, for example, the mass of an analyte (not concentration) is to be detected.
The present disclosure is directed to a mass spectrometer that addresses one or more of these concerns.